व्यापृतेष्विन्द्रियेष्वात्मा व्यापारीवाविवेकिनाम् ।दृश्यतेऽभ्रेषु धावत्सु धावन्निव यथा शशी ॥ १९ ॥
In plain words
When the senses get busy, people who cannot tell the Self from what is not the Self see the Self as the one doing the work. It is like watching the moon on a windy night: the clouds are racing, and the moon looks like it is racing too.
Close to the Sanskrit
When the senses are engaged, the Self appears to those without discrimination as if it were the agent — just as, when the clouds are running, the moon is seen as if running.